Numerical analysis of land subsidence due
to natural compaction of the Upper Adriatic Sea basin
G. Gambolati, P. Teatini
Dept. Mathematical Methods and Models for Scientific
Applications, University of Padova, Padova, Italy
ABSTRACT
We have simulated the evolution of the accreting Quaternary column at
three strategic locations (Venice, Po river delta, Ravenna) along the
Upper Adriatic coastline.
The analysis is performed by a 1-D nonlinear finite element model of
soil compaction driven by groundwater flow in an isothermal sedimentary
basin subject to a continuous vertical sedimentation process.
The constitutive relationship of the most important parameter
controlling the event, i.e. the soil compressibility vs the
effective intergranular stress, has been derived from a number of
oedometer tests carried out on samples taken from shallow and deep
exploratory boreholes scattered through the study area.
Dating of the sediments has allowed for the estimate of an average
depositional rate at selected time intervals spanning the Middle-Upper
Pleistocene, the Holocene and the historical times.
The model has been run so as to reproduce the present day sediment
thickness with a small excess hydrostatic pressure since the Adriatic Sea
basin in known to be normally pressured.
It is assumed that sedimentation in the last 0.5 My was substantially
in equilibrium
with subsidence so that the deposition surface remained at a constant
elevation.
The results of our analysis indicate a natural land settlement in the
next century between 0.5 mm/y at Venice and 4-5 mm/y in the Po
delta, with an intermediate value of 2-2.5 mm/y at Ravenna.
